Most modern stringed instruments are made of wood. One of the limitations of wood as a material is that it is affected by changes in atmospheric humidity. Increased humidity can cause the wood in the instrument to expand. Decreases in humidity can cause the wood of the instrument to contract. Research has shown that relative humidity less than 40% can remove water from the wood in the instrument. These changes will affect the tone of the instrument. These changes can also cause the material of the instrument to fail, especially if the wood in the instrument contracts risking cracking or splitting joints between pieces of wood. In the event that the wood cracks or joints split, the instrument is rendered inoperable. Any musician is aware of the danger of humidity change to their instrument. A number of patents attempt to control the humidity in a musical instrument, but do not have the advantages of the present invention.
U.S. Pat. No. 3,407,700 by Hollander uses a sponge contained within an impermeable case that has holes in it. Water is soaked into the sponge and then the water is allowed to evaporate out the holes of the case into the body of the instrument. The present invention uses a water absorbent material, rather than a sponge. The use of a water absorbent material allows for a greater quantity of water to be used and avoids dripping. This allows for greater control over the humidity within the instrument. Furthermore, the sponge dries out quickly and, in practice, requires daily refills. The amount of water than the sponge can absorb is limited because after a certain amount, liquid water oozes out of the sponge. This results in the liquid water being released into the inside of the instrument, risking warping the wood of the instrument. Finally, the sponge releases water unevenly so that more water is released at first and then less and less water is released over time.
U.S. Pat. No. 5,289,751 by Light uses a water absorbent material contained with a relatively stiff tube made of a vapor permeable material. The problem with a rigid tube is that it makes it difficult to determine if the tube is empty or full. The present invention uses a flexible tube that deflates as it is emptied of water, allowing for easy determination of the quantity of water in the present invention.
U.S. Pat. No. 5,936,178 by Saari is a humidifier for boxes that contain cigars, violins or computer hard drives. U.S. Pat. No. 6,244,432 by Saari is a similar system for use with boxes that contain guns. Saari uses a saturated solution of some solute such as salt or sugar. This solution can be thickened to a material with an additive. The solution is then placed within a pouch of permeable material that releases water vapor to humidify the instrument. The present invention does not use a salt or sugar solution, but uses a material as the water absorbent substance. Furthermore, the Saari patent does not have a way to refill the device. Thus, in dry environments, the Saari patent device will dry out quickly and be rendered useless.
U.S. Pat. No. 6,375,000 by Weder also uses a salt solution. In this case the solution is made of water and a cross-linked polyacrylic acid sodium salt. The sodium salt is in powder or film form and is contained within a porous pouch that have holes too small for liquid water to escape, but large enough for water vapor to escape. The present invention does not use cross-linked polyacrylic acid sodium salt, but uses a water absorbent material such as acrylate polymer. Like the Saari patent, the Weder patent lack a way to refill the device. This will limit the effectiveness of the Weder device in a dry climate, as it will dry out quickly and become useless.
U.S. Pat. No. 5,829,452 by Oster uses a similar gel as the preferred embodiment of the present invention, but is specifically aimed at use with cigar humidors. While Oster does refer to systems that are used to humidify musical instruments in the Background of the Invention section of the Oster patent, Oster does not claim the use of '452 with musical instruments.